This invention relates to a pool cover. More particularly, this invention relates to a solar pool cover.
As is known, various types of pool covers have been employed for covering over swimming pools and the like. In some cases, a tarpaulin-like cover has been employed to cover over a swimming pool when the pool is not in use in order to prevent debris and the like from falling into the water contained within the pool. Typically, these covers are of relative heavy weight construction.
In cases where a swimming pool is heated, use has been made of covers which are constructed to retain as much heat as possible within the body of water within the pool. For example, some pool covers have used a combination of glass and aluminum in an attempt to conserve heat within the pool. However, the use of such materials can be dangerous while being difficult to handle, for example, there is a potential danger of glass breakage while the incompatibility of chlorine with aluminum dictates against the use of such a cover for swimming pool applications.
Other types of pool covers have been of the solar type. For example, U.S. Pat. No. 3,072,920 describes a swimming pool cover for collection or reflection of solar heat in which the cover is made of a sheet of plastic material having a bottom surface covered with a layer of dark-colored material for the absorption of solar energy and an upper surface covered by a reflective surface, such as aluminum. In addition, an over-layer of transparent plastic material is attached to the marginal edge of the plastic sheet to form air-filled compartments or pockets to increase the buoyancy of the cover. In the summer, the cover is to be turned so that the dark absorptive surface is down facing the water with the aluminized surface facing the sky to reflect the sun""s radiant energy. In the winter, the cover is to be reversed so that the dark surface is exposed to solar energy.
U.S. Pat. No. 4,146,015 describes a solar pool heater which employs a membrane having a smooth side and a pebbled side wherein each of the xe2x80x9cpebblesxe2x80x9d is a sealed air pocket. The entire membrane is transparent to permit the transmission of radiant energy to heat the underlying water and pool bottom.
U.S. Pat. No. 4,426,995 describes a solar quilt for heating a swimming pool. The quilt is described as having an upper film formed of semi-hemispherical modules which abut and are sealed to a lower film. The upper film is described as transmissive of downwardly directed solar radiation and reflective of upwardly directed radiant energy in the ultra-violet range. The lower film is said to be absorptive of incident solar energy.
U.S. Pat. No. 4,709,688 describes an opened cell sheeting for use as a covering for swimming pool surfaces. In addition, reference is made to previously known sealed cell pool covers which include an upper plastic sheet with dimples and a plastic sheet bonded to the upper sheet.
U.S. Pat. No. 3,022,781 describes a heater made of plastic film layers wherein a lower layer is made absorbent to radiant energy by being painted black or by incorporating a black pigment within the plastic composition.
U.S. Pat. No. 3,893,443 describes a floating pool heater employing individual unit heaters which are capable of floating. In addition, each unit has a bottom wall with a blackened surface on the inside.
Generally, the previously known structures are of relatively thick, heavy weight construction. Further, in some cases, the covers which have been made of lightweight materials have tended to be of a transparent nature such that heat energy in a covered pool is permitted to radiate out of the pool through the cover during dark periods. Also, where the covers have been transparent, a portion of the heat band is reflected without being converted to heat in the pool water. In addition, algae growth is promoted in and on the pool surfaces due to the passage of light into the water below the cover.
Accordingly, it is an object of the invention to provide a pool cover which has good insulating qualities with enhanced heat transfer into a body of water in a pool.
It is another object of the invention to provide a pool cover which is of light weight construction and which can be easily handled.
It is another object of the invention to provide a pool cover which has an efficient heat transfer quality.
It is another object of the invention to provide a pool cover which can be made of recycled plastic materials.
It is another object of the invention to provide a pool cover which eliminates algae growth while the cover is on a swimming pool.
It is another object of the invention to reduce the need for chemicals in maintaining a swimming pool.
It is another object of the invention to provide a pool cover of low cost construction.
It is another object of the invention to provide less filter run time with corresponding reduced pump run time which, in turn, reduces the amount of electric power needed.
Briefly, the invention provides a pool cover which is comprised of a first layer which may be opaque or which may be translucent for passing sunlight therethrough and a second opaque layer secured to the first layer for blocking sunlight from entering a body of water in a pool to thereby inhibit growth of algae in the body of water. In addition, at least one of the layers has a plurality of pockets therein facing the other layer and which are sealed relative to the other layer to encapsulate air therein.
In the embodiment employing a translucent or transparent layer, the translucent layer would typically be the top layer so that sunlight may pass through the translucent layer to heat the opaque layer and the air in the pockets for transfer of the heat to the pool water under the opaque layer. The air trapped in the pockets forms an insulating barrier for heat attempting to escape up through the cover while the opaque layer eliminates or greatly reduces evaporation from the pool surface.
The cover serves to form an insulating barrier during periods of darkness, such as nighttime hours, or cool day conditions in order to conserve heat within a heated body of water within a swimming pool. This is accomplished in two ways. First, during sunlight hours, the heat rays of the sun impinging on the transparent or translucent top layer pass through and strike the bottom opaque layer and are converted to heat. The circulating pool water then absorbs the heat either by touching the opaque layer or by conduction from the super hot air trapped in the air pockets. Second, the pool cover serves to eliminate evaporation from the pool water while in place on the pool surface.
It has been known that a transparent or translucent cover will help promote the growth of algae due to the light which passes through the cover coupled with the rise in pool water temperature. During daylight hours, the opaque bottom layer of the pool cover blocks the light which is necessary for algae growth. Coupled with the evaporation preventing characteristics of the pool cover, the need for pool chemicals and water replacement becomes greatly diminished.
In the construction where both the top and bottom layers are opaque, sunlight is absorbed by the top layer so that the heat generated within the top layer passes into the air trapped within the pockets as well as to the underlying opaque layer.
In one embodiment, the pockets which may be of semi-spherical shape are formed in the opaque second layer for floating on the body of water.
In another embodiment, a third layer is secured to the bottom of the second layer so that the second layer becomes sandwiched between the top transparent layer and the bottommost third layer.
The construction of the pool cover is such that each layer may be made of a suitable light weight plastic material, such as polyvinyl-chloride, polystyrene, polyethylene or polypropylene. In addition, the overall pool cover is flexible so as to permit rolling up on itself.
Still further, the entire cover may be made of recycled plastic material which is less costly. In this regard, the opaque layer may be made black in color although any other dark color may be used.